There are volcanoes under the ice in Antarctica. It's been 8,000 years since one burst through the ice to the surface, but it could happen again. And the signs are there that it may be sooner than later. Seismic activity is increasing in the frozen continent.

In 2010 and 2011, a team of researchers, led by Washington University graduate student Amanda Lough, detected bursts of seismic activity—at least 1,370 earthquakes centered deep beneath Antarctica’s Marie Byrd Land in the continent’s West Antarctic Ice Sheet. “We interpret the swarm events as deep long-period earthquakes based on their unusual frequency content. Such earthquakes occur beneath active volcanoes, are caused by deep magmatic activity and, in some cases, precede eruptions,” the scientists write in their study.

The sighting of the earthquake swarms isn’t a guarantee of an impending eruption, they say. But swarms have been seen in advance of eruptions before, like in 1991′s Mount Pinatubo eruption. The earthquakes are caused by the changes in pressure exerted on the subsurface rock as magma moves around, deep within the Earth.

An eruption from a Antarctic volcano is no guarantee that it will be seen above the ice -after all, it's a half-mile thick. But an under-ice eruption could cause significant melting and instability of the ice shelf. Read more about the volcanoes of Antarctica at Smithsonian.